I just talked to Interco and found out some real good information concerning the tread depth.
This tire is a Primary Service Application meaning, its intended to be used for RockCrawling but of course, Interco seems to "grab" other terrain types when a new design is molded. It's like the Bogger - "the Bogger is like a Drag tire for Mud". By design, the Bogger is made for forward momentium in Mud and lateral traction is not of concern. It just worked out that these tires also worked in other types of terrain, but you still have to use "Common Sense" when using a tire in terrain other than what it was designed for. You would not dive into a mud pit with your all terrains and expect the same performance as a Bogger would you? Common sense tells me I would not get very far with low void, non cleaning tires in the goo.
Natually Interco progresses with each new design. The "borrow" the ideas that work from other designs in the past and adapt them to their new design. They also listen to the public, heres an example.
About the IROK and its shallower tread depth. Some of the competitors in the Rockcrawling world said they needed the "lightest tire available". Although Interco had a different philosophy on this design, you have to listen to these competitors - they usually know what they need. Where they saved weight? They created higher voids in the tread pattern. They also shallowed up the tread a bit. What did this do? It provided a lighter tire and the open voids allow the tread to grip and find traction better than a tire with lesser voids. Another way they saved weight all the while adding a traction aid - they added side wall lugs, but hollowed them out to save weight. The reason the larger lugs on the sidewalls are curved is so they grip rock better and hold onto it. A straight lug on the side, doesn't tend to grip a rock - they slide off.
Why are the IROK's cheaper than traditional Swampers? When you have higher voids and shallower tread depth, it also makes the price come down. Rubber costs just like a pound of hamburger. The more you get, the more it costs you.
This tire is a bias design, so you will not get that torque split like traditional radials either.
This is information from the source, so take it however you want. /forums/images/graemlins/thumb.gif